Prototyping of patterned functional nanostructures

ABSTRACT

The present invention provides a coating composition comprising: A coating composition comprising: TEOS; a surfactant; at least one organosilane; HCl; water; and ethanol. The present invention also provides films made from such a coating composition and a method for making such films.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. Patent Application:U.S. patent application Ser. No. 09/838,153, entitled “Prototyping ofPatterned Functional Nanostructures” filed Apr. 20, 2001, now U.S. Pat.No. 6,471,761, which claims priority to U.S. Provisional Application No.60/198,756, entitled “Rapid Prototyping of Patterned Organic/InorganicFunctional Nanostructures” filed Apr. 21, 2000. The entire disclosureand contents of the above applications are hereby incorporated herein byreference

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to patterned nanostructures, andmore particularly to patterned functional nanostructures.

2. Description of the Prior Art

Marine organisms like diatoms and radiolaria provide many examples ofintricately organized architectures preserved in silica or calciumcarbonate. Such natural microstructures are formed by biomineralization,a templated self-assembly process in which preorganized organic surfacesregulate the nucleation, growth, morphology and orientation of inorganiccrystals. To date, a variety of synthetic pathways that mimic aspects ofbiomineralization have been explored to prepare patterned ceramicmaterials.

Hierarchical materials assembly strategies have been developed whichallowed growing surfactant-templated mesoporous silica in solution routeon hydrophobic patterns prepared by micro-contact printing (μCP). Thefilms formed by this technique are usually noncontinuous and haveglobular morphologies. In addition it takes days to form nanostructuresusing μCP. Oriented mesoporous silica patterns, using a micro-molding incapillary (MIMIC) technique can be made. However, it requires hours toform such ordered structures under electric field.

Although progress has been made in the preparation of a wide variety ofpatterned ceramic materials, current synthetic methods have severalinherent drawbacks from the standpoint of nanotechnology: First, mosttemplating procedures are conducted in time-consuming batch operationsoften employing hydrothermal processing conditions. Second, theresultant products are typically ill-defined powders, precluding theirgeneral use in thin film technologies. Third, procedures developed todate are often limited to forming patterns of pores.

For many envisioned nanotechnologies, it would be desirable to createpatterned nanocomposites consisting of periodic arrangements of two ormore dissimilar materials. None of the existing technologies provide ameans to fulfill the above need.

Soft lithography approaches have been combined with surfactant andparticulate templating procedures to create oxides with multiple levelsof structural order. However, materials thus formed have been limitedprimarily to oxides with no specific functionality, whereas for many ofthe envisioned applications of hierarchical materials, it is necessaryto define both form and function on several length scales. In additionthe patterning strategies employed thus far require hours or even daysfor completion.

Such a long processing time is not very useful in further developingnanotechnologies because slow processes are inherently difficult toimplement in commercial environments. Hence a rapid method that enablesone to form hierarchically organized structures on substrates in amatter of seconds is highly desirable.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to formhierarchically organized structures on substrates in a matter ofseconds.

It is a further object of the present invention to form patternednanocomposites that will provide materials suitable for use innanotechnologies.

It is a further object of the present invention to form nanocompositematerials exhibiting multiple levels of structural order and function onmultiple length scales.

It is yet another object of the present invention to form homogeneousmesoporous thin-films.

It is yet another object of the present invention to provide a means toform highly oriented particulate mesophases on a substrate.

It is yet another object of the invention to provide approaches totailor materials structure and function on multiple length scales i.e.micro-, meso-, and macro-scopic scales and at multiple locations fordevice fabrications.

According to a first broad aspect, the present invention provides acoating composition comprising: TEOS; a surfactant; at least oneorganosilane; HCl; water; and ethanol.

According to a second aspect of the present invention, there is provideda method for forming a film comprising: providing at least one coatingcomposition comprising: TEOS; a surfactant; at least one organosilane;HCl; water; and ethanol; applying the coating composition on a substrateto form a coating on the substrate; and drying the coating to form apatterned silsequioxane film.

Other objects and features of the present invention will be apparentfrom the following detailed description of the preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a schematic phase diagram for CTAB in water;

FIG. 2A illustrates a steady-state film thinning profile establishedduring dip-coating of a complex fluid comprising soluble silica,surfactant, alcohol, and water;

FIG. 2B illustrates the approximate trajectory taken inethanol/water/CTAB phase space during dip-coating;

FIG. 3 shows the chemical formulas of bridged silsesquioxane monomers1-3 used in accordance with a preferred embodiment of the presentinvention;

FIG. 4 is a schematic illustration of a detergent phase diagram usingsurfactant-oil-water combination;

FIG. 5A is a schematic illustration of self-assembly oforganic-inorganic nanolaminates during dip-coating showing thehypothetical arrangement of surfactant, monomer, crosslinker, andinitiator adjacent to an oligomeric silica layer;

FIG. 5B illustrates the hypothetical structure of covalently bondedsilica/poly (dodecylmethacrylate) nanocomposite;

FIG. 6 is a table listing various functional organosilanes andproperties of resultant thin films made according to the method ofpresent invention;

FIG. 7A illustrates micro-pen lithography of a surfactant-templatedmesophase utilizing a coating composition of the present invention;

FIG. 7B illustrates the steep 3-D evaporation-induced concentrationgradient in a 3-D, binary fluid pattern made using a coating compositionof the present invention dispensed on a flat surface using the method ofthe present invention;

FIG. 8 illustrates the scheme of patterned functional mesostructureformed by selective de-wetting using micro-contact printing orelectrochemical desorption technique using the method of presentinvention;

FIG. 9 illustrates X-ray diffraction results of the uncalcined andcalcined thin-film mesophases prepared using ethylene-bridgedpolysilsesquioxane;

FIG. 10A is a TEM micrograph of a mesophase prepared using the method ofthe present invention;

FIG. 10B is a TEM micrograph of another mesophase prepared using themethod of the present invention;

FIG. 10C is a TEM micrograph of another mesophase prepared using themethod of the present invention;

FIG. 10D is a TEM micrograph of another mesophase prepared using themethod of the present invention;

FIG. 11 shows a surface acoustic wave based nitrogen sorption isothermof the calcined thin-film mesophase prepared using two differentsurfactants using the method of the present invention;

FIG. 12 is a table listing the properties of calcinedTEOS//(≡Si—(CH₂)₂—Si≡) mesoporous thin-films made according to themethod of present invention;

FIG. 13A is an optical micrograph of patterned rhodamine-B containingsilica mesophase made according to the method of the present invention;

FIG. 13B is a representative TEM micrograph of a fragment of a patternedrhodamine-B containing film made according to the method of the present;

FIG. 14A is an optical micrograph of a dot array created by ink jetprinting of standard ink on a non adsorbent surface in accordance withthe method of the present invention;

FIG. 14B is an optical micrograph of an array of hydrophobic, mesoporoussilica dots created by evaporation-induced silica/surfactantself-assembly during ink jet printing according to the method of thepresent invention;

FIG. 14C shows an optical micrograph of an array of hydrophobic,mesoporous silica dots created by evaporation-induced silica/surfactantself-assembly during ink jet printing according to the method of thepresent invention;

FIG. 15A is a fluorescence image of three adjacent 5,6 FAM,SE-conjugated pore channel networks after introduction of aqueoussolutions prepared at pH 4.8, 7.7, and 12.0;

FIG. 15B is a fluorescence spectra of 5,6 FAM, SE-conjugated mesoporousfilms made according to the method of the present invention uponexposure to aqueous solutions prepared at pH 4.8, 7.7, or 12.0 and afluorescence spectra of 0.1 μm solutions at the corresponding pH's forcomparison;

FIG. 15C is a cross-sectional TEM micrograph of the patterned, dyeconjugated thin film mesophase, providing evidence of the 3-D porechannel network in the film made according to the method of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

It is advantageous to define several terms before describing theinvention. It should be appreciated that the following definitions areused throughout this application.

Definitions

Where the definition of terms departs from the commonly used meaning ofthe term, applicant intends to utilize the definitions provided below,unless specifically indicated.

For the purposes of the present invention, the term “organic additive”refers to functional molecules, polymers, or biomolecules.

For the purposes of the present invention, the term “dye” refers to anydye including molecules that exhibit fluorescent colors.

For the purposes of the present invention, the term “organosilane”refers to any compound having the general formula R′Si(OR)₃ wherein R′is a non-hydrolyzable organic functional ligand. When the term“organosilane” is used in reference to coating compositions of thepresent invention, the term “organosilane” refers to a an organosilaneother than TEOS.

For the purposes of the present invention, the term “aminoorganosilane”refers to an organosilane having a non-hydrolyzable organic functionalligand including an amino.

For the purposes of the present invention, the term “nanotechnology”refers to is technology employing nanostructures.

For the purposes of the present invention, the term “nanostructure”refers to structures in the range of 1-1000 nm. These structures are atthe confluence of the smallest of human-made devices and the largemolecules of living systems.

For the purposes of the present invention, the term “nanoscale scienceand engineering” refers to the fundamental understanding and resultingtechnological advances arising from the exploitation of new physical,chemical and biological properties of systems that are intermediate insize, between isolated atoms and molecules and bulk materials, where thetransitional properties between the two limits may be controlled.

For the purposes of the present invention, the term “evaporation-inducedself-assembly” refers to spontaneous organization of materials throughnon-covalent interactions induced by evaporation.

For the purposes of the present invention, the term “nanocompositematerial” refers to nanoscale composite materials in which differentmaterials are mixed or combined together through physical or chemicalinteractions.

For the purposes of the present invention, the term “pattern” refers toprototype or structure of matter organization of a material such as afilm. This organization may be at atomic level, at molecular level or atmacromolecular level.

For the purposes of the present invention, the term “mesophase” refersto surfactant molecules or block copolymers that can form micelles orliquid crystalline phases in water. These liquid crystalline phasesinclude lamellar, hexagonal, cubic structures. The length scale of thesestructures is a range of 1 nm-50 nm. These liquid crystalline phases arealso referred to as mesophase.

For the purposes of the present invention, the term “thin-film” refersto films having a thickness 50 nm-1 μm.

For the purposes of the present invention, the term “mesoporous” refersto porous material having pores in the size range of 1 nm to 50 nm.

For the purposes of the present invention, the term “sol-gel dipcoating” refers to a method of preparing thin films where the film isformed on the surface of the silica substrate as a result of theevaporation of the solvent from the solution used to dip the silicasubstrate.

For the purposes of the present invention, the term “three-dimensionalnetwork” refers to a structure in which matter organizes in x, y, zspace.

For the purposes of the present invention, the term “matter” refersatoms, molecules and macromolecules.

For the purposes of the present invention, the term “accessible” refersto orientation of the pores organized in a direction perpendicular tothe base of the film such that the incoming reactants applied to thesurface of the film can enter these pores.

For the purposes of the present invention, the term “featureless” refersto films that lack rough surfaces and discontinuities in other wordsfilms that are smooth and homogeneous.

For the purposes of the present invention, the term “conformation”refers to the various patterns present in thin films or nanocompositesmade by evaporation-induced self-assembly based processes such assol-gel dip coating, micro-pen lithography and ink jet printing. As theprocess progresses the patterns change from being micelles→micellarcomposites→periodic pores→hexagonal→cubic lamellar→vesicular etc. Allthese patterns represent progressive changes in conformations of thinfilms or nanocomposites.

For the purposes of the present invention, the term “hierarchicalmaterial” refers to material having multiple structures and multiplefunctions.

For the purposes of the present invention, the term “molecular scale”refers to sizes in the range of 1 Å to 10 nm.

For the purposes of the present invention, the term “mesoscale” refersto sizes in the range of 1 nm-1000 nm.

For the purposes of the present invention, the term “macroscale” refersto sizes in the range of 1000 nm to 1 mm.

For the purposes of the present invention, the term “structure” refersto the unit or arrangement or organization of matter through chemicalbonds or physical interaction.

For the purposes of the present invention, the term “function” refers tothe abilities or properties of matter. For e.g. The materials may havethe ability to respond by changing color to changes in pH, temperature,pressure and humidity respectively. These materials would then be calledto have the functionality of pH sensitivity, thermo sensitivity,pressure sensitivity and moisture sensitivity respectively; or abilityto absorb metal ion or particles; or have hydrophobic or hydrophilicproperties.

For the purposes of the present invention, the term “homogeneous” refersto a solution where all the components of the solution are evenlydistributed resulting in no discontinuities.

For the purposes of the present invention, the term “calcined” refers tothe process of heating the mesophase at high temperatures in the rangeof 300° C. to 400° C. in presence of different gases to harden thesilica structure and “uncalcined” refers to the mesophase that has notbeen hardened by heating in the above manner.

For the purposes of the present invention, the term micro-penlithography refers to patterns made by a micro-pen approach.

For the purposes of the present invention, the term “ink jet printing”refers to any conventional ink jet printing process and any process forthe controlled deposition of droplets of a liquid composition or ink ona substrate. In general ink jet printing deposits a droplets of a liquidcomposition in a pattern controlled by a computer or other controldevice.

For the purposes of the present invention, the term “selectivede-wetting” refers to deposition of a coating composition/film only onone or more selective regions. For example a sol solution may onlydeposit on a hydrophilic region.

Description

The use of new technologies based on nanoscale machines and devices willplay an increasing role in the future. Key to the realization of thisnanotechnology world are simple, efficient methods of organizingmaterials such as molecules, molecular clusters, polymers, or generallyspeaking, building blocks into precise, predetermined nanostructuresthat may be preserved in a robust engineering form.

One way of forming nanostructures is through the self-assembly ofamphiphillic surfactant molecules or polymers composed of hydrophobicand hydrophilic parts into well-defined supramolecular assemblies. FIG.1 is a schematic phase diagram for cetyl trimethyl ammonium bromide(CTAB) in water. X-axis shows the increasing surfactant-CTABconcentration expressed as weight percent. Temperature in ° C. isrepresented by the Y-axis. The arrow denotes evaporation-driven pathwayduring dip-coating, aerosol processing. FIG. 1 shows a solution of CTABin aqueous solution above the critical micelle concentration (cmc),surfactants assemble into micelles, spherical or cylindrical structuresthat maintain the hydrophilic parts of the surfactant in contact withwater while shielding the hydrophobic parts within the micellarinterior. Further increases in surfactant concentration result in theself-organization of micelles into hexagonal, cubic, or lemellarmesophase. Such detergent mesophases do not themselves represent robustengineering materials suitable for nanotechnologies.

About a decade ago it was discovered that surfactant self-assemblyconducted in aqueous solutions of soluble silica species results inspontaneous co-assembly of silica-surfactant mesophases. Surfactantremoval creates periodic mesoporous solids essentially silica fossils ofthe liquid-crystalline (LC) assembly. Over the last few years this workhas been extended to produce a wide compositional range of mesoporoussolids, and using a variety of surfactants, the pore sizes have beenvaried in the range of 1 nm to over 10 nm. Despite excellent control ofpore size, early mesoporous materials were made in the form of powders,precluding their use in thin film applications like membranes, lowdielectric constant inter-layers, and optical sensors.

Stable, supported, mesoporous silica films were made where substrateswere introduced into silica/surfactant/solvent systems used to preparebulk hexagonal mesophases. The initial surfactant concentrationsc_(o)>cmc. Under these conditions, hexagonal silica-surfactantmesophases are nucleated on the substrate with pores oriented parallelto the substrate surface. Growth and coalescence over a period of hoursto weeks resulted in continuous but macroscopically inhomogeneous filmscharacterized by granular structures on micrometer-length scales.

In addition, by condensation of tetrafunctional silanes (Si(OR)₄) withtrifunctional organosilanes ((RO)₃SiR′) or by inclusion of organicadditives, the present invention selectively derivitizes the silicaframework with functional R′ ligands or molecules. The resultingmaterials exhibit structure and function on multiple length scales: onthe molecular scale, functional organic moieties are positioned on poresurfaces, on the mesoscale, mono-sized pores are organized into 1-, 2-,or 3-dimensional networks, providing size-selective accessibility fromthe gas or liquid phase, and on the macroscale, 2-dimensional arrays andfluidic or photonic systems may be defined.

A general definition of self-assembly is the spontaneous organization ofmaterials through noncovalent interactions such as hydrogen bonding, Vander Waals forces, electrostatic forces, ττ—ττ interactions, etc. with noexternal intervention. Self-assembly typically employs asymmetricmolecules that are pre-programmed to organize into well-definedsupramolecular assemblies. Most common are amphiphilic surfactantmolecules or polymers composed of hydrophobic and hydrophilic parts. Inaqueous solution above the critical micelle concentration (cmc),surfactants assemble into micelles, spherical or cylindrical structuresthat maintain the hydrophilic parts of the surfactant in contact withwater while shielding the hydrophobic parts within the micellar interioras shown in FIG. 1. Further increases in surfactant concentration resultin the self-organization of micelles into periodic hexagonal, cubic, orlamellar mesophases as shown in FIG. 1.

An alternative route to the formation of thin film mesophases issuggested in the context of sol-gel dip coating by careful considerationof the parameters that play a role in evaporation driven pathway.Beginning with a homogenous solution of soluble silica and surfactantprepared in ethanol/water solvent with c_(o)<<cmc, preferentialevaporation of ethanol concentrates the depositing film in water andnonvolatile surfactant and silica species.

FIG. 2A shows a steady-state film thinning profile established duringdip-coating of a complex fluid comprising soluble silica, surfactant,alcohol, and water. FIG. 2A is a plot that has the thickness of the filmin μm plotted along X-axis. The Y-axis on left side shows the distanceabove the reservoir in mm where concentration of the surfactant is beingmeasured. The Y-axis on right side shows the time in seconds above thereservoir needed for dip coating. The X-axis on top of the plot showsthe surfactant concentration in moles/liter. The progressivelyincreasing surfactant concentration drives self-assembly ofsilica-surfactant micelles and their further organization into LCmesophases. Pre-existing, incipient silica-surfactant mesostructures,which exist at solid-liquid and liquid-vapor interfaces at c<cmc, serveto nucleate and orient mesophase development. The result is rapidformation of thin film mesophases that are highly oriented with respectto the substrate surface.

FIG. 2B shows that through variation of the initialalcohol/water/surfactant mole ratio it is possible to follow differenttrajectories in composition space and to arrive at different finalmesostructure. The left corner of the triangle represents 100% water,the right corner of the triangle represents 100% CTAB and the tip of thetriangle represents 100% ethanol. Point A at the top of the trianglecorresponds to the initial composition of entrained solution, point B isnear the drying line, and point C corresponds to the dried film. Thedashed line in the FIG. 2B represents composition concentration duringdip-coating. The double dashed line represent the region of certainmesophases. The solid arc at the CTAB corner of the triangle representsanother region of mesophases. The two solid lines radiating from thesolid arc represent yet another region of mesophases. Using CTAB,formation of 1-D hexagonal, cubic, 3-D hexagonal and lemellarsilica-surfactant mesophases have been demonstrated In solution (orbelow point A) surfactant exists as a free molecule. During dip-coating,the solvent evaporates. Above dash line the surfactant micelle isformed. Above the drying line the film is formed with differentmesophases dependent on the initial surfactant concentration within thecoating solution.

The dip-coating scheme depicted in FIGS. 2A and 2B represents a rapid,dynamic self-assembly process that is completed in 10 sec, conducted ina rather steep concentration gradient. Its steady, continuous naturepromotes continuous accretion of micellar or perhaps LC species ontointerfacially organized mesostructures. Large, LC domains growprogressively inward from the solid-liquid and liquid-vapor interfacesas depicted in FIG. 2B with increasing distance above the reservoirsurface. Deposited films are optically transparent and completelyfeatureless on the micrometer-length scale.

The ability to rapidly organize thin film mesophases is based onsuppression of inorganic polymerization during the coating operation.For silicates this is achieved under acidic conditions at a hydroniumion concentration corresponding closely to the isoelectric point ofcolloidal silica ([H₃O⁺]˜0.01). By first turning off siloxanecondensation, the cooperative silica-surfactant self-assembly is allowedto proceed unimpeded, and the resulting as-deposited films exhibit LC orsemi-solid behavior. Subsequent aging, exposure to acid or basecatalysts, or thermal treatment solidifies the silica skeleton, therebylocking in the desired mesostructure.

Evidence for the LC nature of as-deposited films is several-fold: First,using a cantilever beam technique it has been demonstrated that thetensile stress developed during mesophase thin film deposition is in therange of 5-10 MPa. This tensile strength is dramatically less comparedto deposition of the same silica sol prepared without surfactants whichhas the tensile strength of ˜200 MPa. This virtual absence of dryingstress suggests that the film completely dries prior to solidificationi.e., as-deposited films are not solidified. Second, it has beendemonstrated that as-deposited mesophase films may be transformed tocompletely different mesophases e.g., lamellar→cubic. Third, theas-deposited films exhibit self-healing tendencies. These combined LCcharacteristics make the EISA process robust yet versatile.

Transmission electron micrographs (TEM) of calcined film prepared fromCTAB, show large oriented domain of cubic mesophase. Such cubicmesophases are crucial for applications like membranes and sensorsbecause they guarantee pore accessibility and through-film poreconnectivity.

An EISA procedure has allowed preparation of poly i.e. bridgedsilsesquioxane thin-film and particulate mesophases that incorporateorganic moieties into periodic, mesostructured frameworks as molecularlydispersed bridging ligands. Capacitance-voltage measurements along witha variety of structural characterization procedures were performed tobegin to elucidate structure-property relationships of this new class ofsurfactant-templated mesophases. A consistent trend of increasingmodulus and hardness and decreasing dielectric constant withsubstitution of the bridged silsesquioxane (≡Si—(CH₂)₂—Si≡) for siloxane(≡Si—O—Si≡) in the framework is observed. This evidence suggested thatthe introduction of integral organic groups into the frameworks ofmesoporous materials may result in synergistic properties, promising anunprecedented ability to tune properties and function.

The development of organic modification schemes to impart functionalityto the pore surfaces has received much attention since the discovery ofsurfactant-templated silica mesophases. Most recently, using the generalclass of compounds referred to as bridged silsesquioxanes(RO)₃Si—R′—Si—(OR)₃, formation of a new class of poly i.e. bridgedsilsesquioxane mesophases (BSQMs) with integral organic functionalityhas been reported. FIG. 3 illustrates three bridged silsequioxanemonomers 1, 2 and 3 that have been used to form BSQMs.

In contrast to previous hybrid mesophases in which organic ligands ormolecules are situated on pore surfaces, this class of materialsnecessarily incorporates the organic constituents into the framework asmolecularly dispersed bridging ligands. Although anticipation was thatthis new mesostructural organization should result in synergisticproperties derived from the molecular-scale mixing of the inorganic andorganic components, few properties of BSQMs were measured. In addition,samples prepared to date formed granular precipitates, precluding theiruse in applications such as membranes, fluidics, and low-k dielectricfilms needed for all foreseeable future generations of microelectronics.An EISA procedure of the present invention provides a method to prepareBSQM films and spherical nanoparticles. Capacitance-voltage measurementsalong with a variety of structural characterization procedures wereperformed to begin to elucidate structure-property relationships of thisnew class of thin-film and particulate mesophases.

The initially reported syntheses of BSQMs involved precipitation inbasic aqueous media followed by aging for periods up to several days. Toform homogeneous films two requirements are there. Precipitation is tobe avoided and self-assembly process is to be accomplished within thebrief time span of the dip- or spin-coating operation lasting at mostseveral seconds. To meet these requirements, a dilute, homogeneous,ethanolic solution is prepared that suppress silica/surfactantself-assembly and employ acidic conditions that retard siloxanecondensation. The details of this EISA procedure of the presentinvention that provides a method to prepare BSQM films and sphericalnanoparticles that incorporate organic moieties into periodic,mesostructured frameworks as molecularly dispersed bridging ligands aredescribed in Example 1 below.

Nanocomposite self-assembly represents an extension of the EISA processdescribed above. Using the generic detergent phase diagram shown in FIG.4 as a conceptual guide, oil is used to represent a wide variety ofhydrophobic, organic precursors and reagents such as monomers,crosslinkers, oligomers, functionalized polymers, initiators, etc. In aprocess not so unlike washing dishes, micelle formation is used tospatially separate and organize organic precursors and inorganicprecursors. These organic precursors are sequestered within thehydrophobic micellar interiors and inorganic precursors are organizedaround the hydrophilic micellar exteriors. Further self-organization ofmicelles into periodic hexagonal, cubic, or lamellar mesophasessimultaneously positions both the organic and inorganic precursors intoprecise 3-D arrangements. Combined organic/inorganic polymerizationlocks in the nanocomposite architecture and covalently bonds theorganic/inorganic interface. The beauty of nanocomposite self-assemblyapproach of the present invention is its simplicity and efficiency: itprovides a method to rapidly prepare laminated organic/inorganiccomposites since many hundreds of alternating organic/inorganic layerscan be assembled in seconds.

Nanocomposite self-assembly is driven by evaporation during filmdeposition. Schematic illustration of self-assembly of organic-inorganicnanolaminates during dip-coating is shown in FIG. 5A. Nanocompositeself-assembly begins with a homogeneous solution of soluble silicates,surfactant, organic monomers, and photo or thermal initiators preparedin ethanol/water solvent with c_(o)<cmc. During coating, preferentialevaporation of ethanol that is used initially to solubilize the organicprecursors and homogenize the solution, progressively enriches theconcentrations of water, HCl and the nonvolatile solution constituentswithin the depositing film. The increasing concentrations of surfactantand water cause the surfactant concentration to exceed the cmc,resulting in micelle formation and concurrent partitioning of theorganic precursors and initiators into the micellar interiors and theinorganic precursors surrounding the micellar exteriors. As confirmed byoptical probe studies, see FIG. 5A, continued evaporation promotesco-assembly of these species into LC mesophases, thereby simultaneouslyorganizing both the organic and inorganic precursors into the desiredlaminated form. Photo or thermally induced polymerization of the organicmonomers and continued inorganic polymerization complete the compositeassembly process as shown in FIG. 5B.

In a preferred embodiment, the present invention provides a method forforming a patterned silsequioxane film by applying a coating compositioncomprising: TEOS; a surfactant; at least one organosilane; HCl; water;and ethanol on a substrate to form a coating and then drying the coatingto form a patterned silsequioxane film. Preferably, no additionalheating is required to form a film of the present invention.

Preferred organosilanes for use in the method of the present inventioninclude: tridecafluoro-1,1,2,2,-tetrahydrooctyltriethyoxysilane (TFTS),mercaptopropyltrimethyoxysilane (MPS), aminoorganosilane,aminopropyltrimethyoxysilane (APS), (H₅C₂O)₃SiCH₂CH₂Si(OC₂H₅)₃; and3-(2,4,-dinitrophenylamino)propyltriethoxysilane has the followingformula:

Other organosilanes may also be used in the coating composition andmethod of the present invention including: cytochrome c, oil blue N,etc. In addition, dye coupled organosilanes may be used in the method ofthe present invention such the dye coupled dyecoupled-aminopropyltrimethyoxysilane. Suitable dyes for coupling with anorganosilane include: rhodamine B, molecules with active esters,carboxylic acid, or isothiocyanantes groups, etc.

As shown Table 1 of FIG. 6 the incorporation of the listed organosilanesinto thin films results in films containing pores organized in3-dimensional networks or cubic arrangements. The pore sizes of themesophases made with the above organosilanes range from 21 Å to 40 Å.

In one preferred coating composition of the present invention, the ratioof Si:ethanol:water:HCl:surfactant:organosilane is1:22:5:0.004:0.093-0.31:0.039-0.8:2.6×10⁻⁵. In another preferred coatingcomposition of the present invention in which an organic additive isused, the ratio of Si:ethanol:water:HCl:surfactant:organosilane:organicadditive is 1:22:5:0.004:0.093-0.31:0.039-0.8:2.6×10⁻⁵. When the coatingcomposition uses the organosilane (H₅C₂O)₃SiCH₂CH₂Si(OC₂H₅)₃ the ratioof Si:EtOH:H₂O:HCl:surfactant is preferably 1:22:5:0.004:0.054-0.18.

The surfactant of the present invention may be a cationic surfactant, anonionic surfactant or an anionic surfactant. A preferred cationicsurfactant is cetyltrimethyl ammonium bromide (CTAB). A preferrednonionic surfactant is Brij-56 (polyoxyethylene cetylether). A preferredanionic surfactant is sodium-dodecyl sulfate (SDS). Other surfactantsthat may be used in the present invention include amphiphilic blockcopolymers, such as pluronic copolymers.

Preferred organic additives for use in the composition or method of thepresent invention include: dyes, such as rhodamine B, oil blue N,cytochrome c, etc.

The coating composition of the present invention may be applied to asubstrate in a variety of ways, depending on the how the film formedfrom the coating will be used. For example, the coating composition maybe applied to a substrate by dip coating, spin coating, micro-penlithography, ink jet printing, etc. When multiple coating compositionsare applied to a substrate using ink jet printing, different coatingsmay be stored in different compartments of the inkjet cartridge of theink jet printer used to apply the coatings. A preferred ink jet printerfor use in the method of the present invention is the HP DeskJet 1200C,however, various types of ink jet printers may be adapted for use in themethod of the present invention.

In preparing the coating composition of the present invention, aninitial composition is formed by mixing TEOS, ethanol, water and HCltogether. The initial composition is then preferably heated to atemperature of at least 60° C. for at least 90 minutes. In a preferredembodiment, the initial composition contains TEOS, ethanol, water andHCl in the mole ratio of 1:3.8:1:5×10⁻⁵. Next, the initial compositionis diluted with ethanol to form an ethanol-diluted composition. In apreferred embodiment, the initial composition is diluted at the ratio of2 volumes of ethanol for every 1 volume of initial composition. Theethanol-diluted composition is then diluted with water and HCl toprovide an acidic sol. An organosilane is then added to the acidic solto form a proto-composition. Finally, a surfactant is added to theproto-composition to form a coating composition of the presentinvention. Preferably, the coating composition has a surfactantconcentration of 0.04 to 0.23 M. An organic additive may also be addedto the coating composition by adding the organic additive to the acidicsol along with the organosilane.

For many applications, it is desirable to remove the surfactant from thefilm of the present invention. The surfactant may be removed from thefilm by heating the film at a temperature of at least 300° C. to 500° C.for a period of 5 to 300 minutes, this process called calcinationsremoves the surfactant and also hardens the silica. Depending on thetype of film and surfactant used, the removal of surfactant may be donein a N₂ atmosphere, an O₂ atmosphere, air, H₂/N₂mixed atmosphere, etc.

In order to reduce water adsorption on the film, the film of the presentinvention may be vapor-treating with a compound such ashexamethyldisilazane. Other suitable compounds that may be used to treatthe film of the present invention to reduce water adsorption includemethyltrichlorosilane.

The present invention will now be described by way of example.

EXAMPLE 1

The rapid patterning procedures of the present invention use of stable,homogenous coating compositions that upon evaporation undergoself-assembly to form the desired organically-modified silica-surfactantmesophase. In one experiment to demonstrate how a film of the presentinvention could be formed, a solution was prepared for this purposecontains oligomeric silica sols in ethanol/water solvents at a hydroniumion concentration ([H₃O⁺]˜0.01) designed to minimize the siloxanecondensation rate, thereby enabling facile silica/surfactantself-assembly during the brief time span of the writing operationlasting maximum up to several seconds. Surfactants were added at aninitial concentration c_(o) much less than the critical micelleconcentration cmc, insuring homogeneity and longevity of the coatingcomposition.

As a pattern of coating composition was delivered onto a surface,preferential evaporation of ethanol causes enrichment of water,surfactant, and silicates, establishing a complex 3-D gradient i.e. agradient extending both in longitudinal and radial directions, in theirrespective concentrations. FIGS. 7A and 7B provides a schematicillustration of micro-pen lithography (MPL) of a surfactant-templatedmesophase. The 3-D finite element simulation of pen lithography is shownin FIG. 7A. Section 1 of the coating composition that has been deliveredonto substrate is very close to the pen orifice has a c_(o)<<cmc andcoating composition 702 is liquid. Section 2 is slightly further awayfrom the pen orifice from which the coating composition is beingdelivered. Section 2 represents the zone where preferential evaporationof ethanol causes enrichment of water, surfactant, and silicates and cmcis exceeded, cooperative silica/surfactant self-assembly createsmicelles on surface 704 of coating composition 706. Further evaporation,predominantly of water promotes the continuous self-organization ofmicelles into silica/surfactant LC mesophases as seen in 708.

Incipient LC domains are nucleated at liquid-vapor interfaces at c<cmcand grow inward along compositional trajectories established by thesteep, 3-D evaporation-induced concentration gradient shown in FIG. 7B.

Films according to the present invention were made using the followingorganosilanes: tridecafluoro-1,1,2,2,-tetrahydrooctyltriethyoxysilane,mercaptopropyltrimethyoxysilane, aminoorganosilane,aminopropyltrimethyoxysilane, (H₅C₂O)₃SiCH₂CH₂Si(OC₂H₅)₃; theorganosilane of Formula (A) described previously; dyecoupled-aminopropyltrimethyoxysilane. Data about the films formed usingthe above-listed organosilanes is shown in Table 1 in FIG. 6.

The amphiphilic nature of some organosilanes like TFTS listed in Table 1of FIG. 6, causes them to behave as co-surfactants, positioning thehydrophilic Si(OR),(OH)_(3-x) headgroups in close proximity to thesilica oligomers where they are incorporated into the framework uponfurther hydrolysis and condensation, thereby localizing covalentlyattached R′ moieties on the pore surfaces. Hydrophobic butalcohol-soluble organic molecules like rhodamine-B partition into thehydrophobic micellar interiors upon ethanol evaporation and ultimatelybecome compartmentalized within the channel network of the resultingmesophase. Retention of the covalently-attached functional organicmoieties after surfactant removal by pyrolysis was confirmed using ²⁹Siand ¹³C magic angle spinning NMR spectroscopy. Fluorescence-imaging andUV-visible spectroscopy were used to confirm retention and functionalityof optically-active ligands and molecules.

The MPL line width can vary from micrometers to millimeters. It dependson such factors as pen dimension, wetting characteristics, evaporationrate, capillary number and ratio of the rates of coating compositionsupply and withdrawal. Where capillary number Ca=coating compositionviscosity×substrate speed/surface tension and withdrawal=inletvelocity/substrate velocity. The effect of wetting has been demonstratedby performing MPL on substrates pre-patterned with hydrophobic,hydrophilic or mixed SAMs. Generally, line widths are reduced byincreasing the contact angle and by reducing the pen orifice dimensionand inlet/substrate velocity ratio.

The advantages of MPL are that any desired combination of surfactant andfunctional silane may be used as coating composition to printselectively different functionalities at different locations.Furthermore, computer-aided design (CAD) may be used to define arbitrary2-D patterns that can be written on arbitrary surfaces. For example,writing rhodamine containing mesophases (refractive index n=1.2-1.3) onaerogel and emulsion-templated thin films (n=1.03-1.10) has beendemonstrated. Such rhodamine containing mesophases may be useful forlasing applications.

When the mesostructure is doped with the laser dye, e.g., rhodamine 6G,amplified spontaneous emission is observed. This is attributed to themesostructures' ability to prevent aggregation of the dye molecules evenat relatively high loadings within the organized high surface areamesochannels of the waveguides.

MPL is best suited to write continuous patterns. Patterned macroscopicarrays of discrete mesostructures can be obtained readily by combiningEISA with aerosol processing schemes like ink-jet printing IJP. The IJPprocess dispenses the coating composition prepared as for MPL asmonosized, spherical aerosol droplets. Upon impaction the droplets adopta new shape that balances surface and interfacial energies. Accompanyingevaporation creates within each droplet a gradient in surfactantconcentration that that drives radially-directed silica/surfactantself-assembly inward from the liquid-vapor interface. The link to CAD,greater printing resolution achieved compared to standard ink, and themethod of the present invention provides an ability to selectivelyfunctionalize the coating composition suggests applications in sensorarrays and display technologies.

MPL and IJP are serial techniques. In situations where it is desirableto create an entire pattern with the same functionality, it might bepreferable to employ a parallel technique in which the depositionprocess occurred simultaneously in multiple locations.

FIG. 8 illustrates dip-coating on patterned SAMs. This rapid, parallelprocedure uses micro-contact printing or electrochemical patterning ofhydroxyl- and methyl-terminated SAMs to define hydrophilic andhydrophobic patterns on the substrate surface. Then using coatingcompositions identical to those employed for MPL and IJP, preferentialethanol evaporation during dip-coating enriches the depositing film inwater, causing selective de-wetting of the hydrophobic regions andensuing self-assembly of silica-surfactant mesophases exclusively on thehydrophilic patterns. In this fashion, multiple lines, arrays of dots,or other arbitrary shapes can be printed in seconds. Recent densityfunctional theory calculations have established the ultimate resolutionof this differential wetting technique to be 1-2-nm.

Overall the evaporation-induced self-assembly process described here andits elaboration in three different printing procedures of the presentinvention holds great promise for rapid prototyping of functionalfluidic and photonic devices along with displays and sensor arrays.Compared to alternative approaches like MMIC, printing is considerablyfaster as the printing takes seconds versus 12 hours needed for MMJC andavoids the need for molds, masks, and resists. Finally by using aspectrum of functional coating compositions and interfacing withcommercially available software, CAD and rapid transcription offunctional micro-systems may soon be a reality.

Method of Preparing Coating Composition Used in the Present Invention

Precursor solutions used as coating compositions were prepared byaddition of surfactants (cationic, CTAB; CH₃(CH₂)₁₅N⁺(CH₃)₃Br⁻ ornon-ionic, Brij-56; CH₃(CH₂)₁₅—(OCH₂CH₂)₁₀—OH), organosilanes(R′Si(OR)₃, as shown in Table 1 of FIG. 6), or organic molecules (listedin Table 1 of FIG. 6) to an acidic silica sol prepared from TEOS[Si(OCH₂CH₃)₄]. The acid concentration employed in the synthesisprocedure was chosen to minimize the siloxane condensation rate, therebypromoting facile self-assembly during printing. In a typicalpreparation, TEOS [Si(OCH₂CH₃)₄], ethanol, water and dilute HCl (moleratios: 1:3.7:1:5×10⁻⁵) were refluxed at 60° C. for 90 min. The sol wasdiluted with 2 volumes of ethanol followed by further addition of waterand HCl. Organosilanes (R′Si(OR)₃, where R′ is a non-hydrolyzableorganic functional ligand, were added followed by surfactants and otheroptional organic additives listed in see Table 1 of FIG. 6. Surfactantswere added in requisite amounts to achieve initial surfactantconcentrations c_(o) ranging from 0.004 to 0.23 M (c_(o)<<cmc). Thefinal reactant molar ratios were: 1 TEOS:22 C₂H₅OH:5H₂O:0.093-0.31surfactant:0.039-0.7 organosilanes:2.6×10⁻⁵ organic additives.

For the ethane-bridged silsesquioxane, (H₅C₂O)₃SiCH₂CH₂Si(OC₂H₅)₃ theneat precursor was diluted in ethanol and mixed with 1-7 wt % CTAB orBrij-56 surfactant followed by addition of an aqueous solution of HCl.The final reactant molar ratios were:Si:EtOH:H₂O:HCl:surfactant=1:22:5:0.004:0.054-0.17. It should be notedthat co-hydrolysis of organosilanes with TEOS in the initial solpreparation, generally resulted in disordered worm-like mesostructures.After pattern deposition and drying, the surfactant templates wereselectively removed by calcination in a nitrogen atmosphere at atemperature sufficient to decompose the surfactant molecules ˜350° C.without degrading the covalently-bound organic ligands R′. The integrityof the organic ligands R′ was confirmed by ²⁹Si and ²³C MAS NMRspectroscopy or by solvent extraction.

Micropen lithography (MPL) was performed using a Model 400a micropeninstrument purchased from Ohmcraft Inc., Pittsford, N.Y. The pen orificewas 50 μm and the writing speed was 2.54 cm/s. The pattern was designedusing AutoCAD 14 software.

Ink jet printing (IJP) was performed using a Model HP DeskJet 1200Cprinter purchased from Hewlett-Packard Co., San Diego, Calif. Thepattern was designed using Microsoft PowerPoint 97 software.

Dip-coating of patterned (hydrophilic/hydrophobic) substrates wasperformed at a withdrawal speed of 6.6-51 cm/min under ambientlaboratory conditions. Hydrophilic/hydrophobic patterns were created bymicrocontact printing of hydrophobic, n-octadecyltrichlorosilane(CH₃(CH₂)₁₆SiCl₃) SAMs on hydrophillic silicon substrates (hydroxylatednative oxide) or by a technique involving electrochemical desorption ofa hydroxyl-terminated SAM prepared from 11-mercaptoundecanol(HO(CH₂)₁₁SH) from patterned, electrically isolated gold electrodesfollowed by immersion in a 1 mM ethanolic solution of 1-dodecanethiol,CH₃(CH₂)₁₁SH.

The rapid prototyping procedures used in the present invention aresimple, employ readily available equipment, and provide a link betweencomputer-aided design and self-assembled nanostructures. The ability toform arbitrary functional designs on arbitrary surfaces should be ofpractical importance for directly writing sensor arrays and fluidic orphotonic systems.

Application of the method of the present invention results in formationof multi-functional mesoporous silica films and rapid fabrication ofpatterned functional nanostructures. Such multi functional mesoporoussilica films and patterned functional nanostructures will be useful fornumerous applications in the fields of micro-sensor systems,microelectronics, catalysis and waveguides.

EXAMPLE 2

Evaporation-Induced Self-Assembly of Hybrid Bridged Silsesquioxane Filmand Particulate Mesophases with Integral Organic Functionality

In a typical synthesis procedure, requisite amounts of bridgedsilsesquioxane monomers shown in FIG. 3 as 1 (from Gelest and triplydistilled prior to use), 2 (synthesized according to Shea et al. J. Am.Chem. Soc. 1992, 114, 6600-6610), or 3 (synthesized according to Shea etal ibid) were dissolved in ethanol followed by addition of 1-7 wt %surfactant [cationic (CTAB, CH₃(CH₂)₁₅N⁺(CH₃)₃Br⁻), nonionic (Brij-56,C₁₆H₃₃(OCH₂CH₂)₁₀OH), anionic (SDS, C₁₂H₂₅OSO₃ ⁻Na⁺), or block copolymer(P123, H(OCH₂CH₂)₂₀(OCH(CH₃)CH₂)₆₀(OCH₂CH₂)₂₀OH)] and an aqueoussolution of HCl (0.1-1.0 N). The investigated range of startingcompositions was represented by the molar ratiosSi:EtOH:H₂O:HCl:surfactant=1:22:5:0.004:(0.054-0.17). To evaluate theeffect of substitution of bridged silsesquioxanes for siloxanes on theproperties of resultant thin-film mesostructures, a series of films wasprepared with varying ratios of TEOS and (EtO)₃Si—(CH₂)₂—Si(OEt)₃. Forthis series, the starting compositions are represented by the molarratios TEOS:1(n=2):Et0H:H₂O:HCl:surfactant=(0.3-3):1:0.25:0.044:0.7:0.00074. In allcases the initial surfactant concentration (c_(o)) was much less thanthe critical micelle concentration (cmc), implying mesoscale homogeneityof the starting sols.

Films were prepared by spin- or dip-coating, and nanoparticles wereprepared by an aerosol-assisted self-assembly process. In both cases,preferential ethanol evaporation concentrates the sol in water,nonvolatile surfactant, and organically bridged polysilsesquioxanespecies. By choosing the initial acid concentration to retard thecompeting process of siloxane condensation, the progressively increasingsurfactant concentration to drive self-assembly ofpolysilsesquioxane-surfactant micelles and their further organizationinto liquid crystalline mesophases was exploited. Pre-existing,incipient polysilsesquioxane-surfactant mesostructures which exist atsolid-liquid and liquid-vapor interfaces at c<cmc, serve to nucleate andorient the mesophase development. The result was formation of thin-filmor particulate BSQMs that are oriented with respect to the solid-liquidand or liquid-vapor interfaces in several seconds. Through variation ofthe shape of the surfactant along with its charge and initialconcentration, this evaporation-induced self-assembly route can be usedto attain a range of thin-film or particulate mesophases.

FIG. 9 shows X-ray diffraction (XRD) results for thin-film bridgedpolysilsesquioxane mesophases prepared from the ethylene-bridgedsilsesquioxane precursor (1 with n=2) with CTAB, Brij-56, or SDSsurfactant before and after calcination at 250° C. in N₂. The multiplesharp peaks observed for the uncalcined SDS system and the virtualelimination of these peaks after calcination are consistent with an[001]-oriented lamellar thin-film mesophase, as is commonly observed forsilica thin-film mesophases prepared from SDS and TEOS. The CTAB andBrij-56 systems are characterized by single intense peaks that shiftslightly to higher 2θ values (lower d-spacing) upon calcination. Thisbehavior is similar to that observed previously for hexagonal and cubicthin-film mesophases prepared from TEOS or TEOS plus variousorganotrialkoxysilane co-monomers.

TEM micrographs of calcined thin-film specimens evaluated by XRD areshown in FIGS. 10A-D. The striped and hexagonal close-packed texturesobserved for the 6 wt % CTAB-derived film as shown in FIG. 10A arecharacteristic of a one-dimensional hexagonal mesophase with d-spacing≅3.3-3.5 nm, consistent with XRD results. Interestingly, undulations anddefects in the stripe pattern in a plane normal to the substrate surfacewere observed, whereas for hexagonal thin-film mesophases prepared fromTEOS these features were observed only in planes parallel to thesubstrate surface. FIG. 10B shows a cross section of the film preparedwith 4 wt % Brij-56. Based on the hexagonal pattern of spots and the5.3-nm spot-to-spot spacing, the upper right region was interpreted as a[111] orientation of a face-centered cubic structure with a ≅9.1-9.3 nm,consistent with XRD results and previous cubic thin-film mesophasesprepared from Brij-56 and TEOS. FIG. 10C shows the TEM micrograph of acalcined spherical nanoparticle prepared using the phenylene-bridgedprecursor 2 of Table 1 of FIG. 6 with 7 wt % P123 block copolymersurfactant. Regions adjacent to the particle circumference, whichcorrespond to the thinnest regions of the specimen in the imagingdirection, exhibit a hexagonal close-packed texture. This structure wasinterpreted as a hexagonal mesophase composed of close-packedcylindrical pore channels aligned parallel to the particlecircumference. This orientation arises from the initial nucleation ofthe hexagonal mesophase at the air-liquid interface and its growthinward, driven by an evaporation-induced radial concentration gradient.On the other hand, particles prepared from the comparable TEOS/7 wt %P123 system exhibit a multilamellar vesicular mesostructure. FIG. 10Dshows the TEM micrograph of calcined spherical nanoparticles preparedusing precursor 3 of Table 1 of FIG. 6 with 7 wt % P123 block copolymersurfactant. This multilamellar vesicular structure is composed ofconcentric bridged polysilsesquioxane layers containing integral vinylfunctionality.

In combination with TEM results discussed above, the major peak in theCTAB system FIG. 9 were interpreted as the (100) reflection of aone-dimensional hexagonal mesophase with d=3.4 nm. The major XRD peak inthe Brij56 system may be interpreted as a (200) reflection of a cubicmesophase with a=9.2 nm.

The porosity of the thin-film specimens prepared from 1 with 6 wt % CTABor 4 wt % Brij-56 was characterized by nitrogen sorption measurementsperformed on film specimens using a surface acoustic wave (SAW)technique. The SAW N₂ sorption isotherms shown in FIG. 11 arequalitatively consistent with those previously obtained for thecorresponding TEOS-derived films and typical of surfactant-templatedmesophases in general. Based on a cylindrical pore model, the ratio ofthe thickness-normalized pore volume and surface area to calculatehydraulic pore diameters of 1.7 and 2.5 nm were used, respectively, forthe CTAB and Brij-56 films. Retention of the bridging organic ligands inthe calcined specimens was confirmed using ¹³C and ²⁹Si MAS NMRspectroscopy. For powders prepared from organosilane 1 of Table 1 ofFIG. 6 with 6 wt % CTAB, a large ¹³C resonance at 5.2 ppm, correspondingto the ethylene bridge, and a very broad ²⁹Si resonance at −57.5 ppm,corresponding to trifunctional (T) silicons was observed. There was noevidence of tetrafunctional Q silicons at −101 or −107 ppm, implyingcomplete retention of the bridging ligands. For the phenylene-bridgedsystem prepared from 2 with 7 wt % P 123, a ¹³C resonance at 133.4 ppmcorresponding to the phenylene bridge and ²⁹Si resonances at −61.0 and−67.2 ppm, corresponding to T² and T³ species, respectively (where thesuperscript denotes the number of bridging oxygens covalently bonded tothe trifunctional silicon center) was observed. Again, there was noevidence of Q silicons.

To begin to establish structure-porosity relationships, a series offilms from TEOS and organosilane 1 of Table 1 of FIG. 6 (n=2) with molarratios TEOS:organosilane 1 65:25 (TB₁), 50:50 (TB₂), and 25:65 (TB₃)were observed. Synthesis and processing procedures were chosen to createisotropic disordered or wormlike thin-film mesophases with comparablefilm thicknesses that was measured by spectroscopic ellipsometry andporosities that were measured by analyses of SAW-based N₂ sorptionisotherms. After calcination at 350° C. under N₂ to remove thesurfactant templates, all films were vapor-treated withhexamethyldisilazane to avoid water adsorption. Table 2 of FIG. 12compares values of the dielectric constants that were measured using astandard capacitance-voltage technique employing a mercury probe,Young's modulus, and hardness. Young's modulus and hardness werecalculated from nanoindentation measurements at a constant indentationdepth, assuming a Poisson ratio of 0.2. A consistent trend of increasingmodulus and hardness and decreasing dielectric constant withsubstitution of the bridged silsesquioxane (≡Si—CH₂)₂—Si≡) for siloxane(≡Si—O—Si≡) in the framework was observed. This preliminary evidencesuggested that introduction of integral organic groups into theframeworks of mesoporous materials can result in synergistic properties,promising an unprecedented ability to tune properties and function. Thetrend of increasing mechanical performance and decreasing dielectricconstant observed here is of immediate and crucial interest to theburgeoning field of low-k dielectrics.

EXAMPLE 3

Micro-Pen Lithography MPL of a Surfactant-Templated Mesophase.

FIGS. 7A and 7B schematically illustrates direct writing of amesoscopically ordered nanostructure, using micro-pen lithography MPL.Micro-pen lithography MPL of a surfactant-templated mesophase.

FIG. 7A shows the initially homogeneous sol metered on to the movingsubstrate experiences preferential evaporation of alcohol creating acomplex 3-D (longitudinal and radial) gradient in the concentrations ofwater and non-volatile surfactant and silicate species. Progressiveenrichment of silica and surfactant induces micelle formation andsubsequent growth of silica/surfactant mesophases inward from theliquid-vapor interface as recently demonstrated for aerosols.

FIG. 7B shows the simulation of 3-D, binary fluid pattern dispensed on aflat substrate with pen orifice 50.0 μm. substrate speed=2.5 cm/s andfluid injection rate (inlet velocity) 4.0 cm/s. Color contours representevaporation-induced, 3-D gradients in alcohol-composition. Residencetimes for fluid elements entering at the pen orifice and exiting atsection 3 ranged from 0.23-0.30-ms. Fluid was modeled as 54 volume %ethanol and 46 volume % non-volatile phase with Reynolds number 1.25 andCa=0.000733. An ad hoc value of 45 was chosen for the static contactangle. This angle persists at all points on the dynamic contact linebecause of the dominance of surface tension at this low value of Ca.

The numerical method utilized for FIGS. 7A and 7B consisted of a 3Dfinite element discretization of the Navier Stokes equations augmentedwith a three dimensional boundary-fitted mesh motion algorithm to trackthe free surface. Special relations at the 3D dynamic wetting line werealso applied.

EXAMPLE 4

Direct writing of a mesoscopically ordered nanostructure, usingmicro-pen lithography MPL of the present invention was used to createthe meandering patterned mesophase containing rhodamine B. FIG. 13Ashows the optical micrograph of patterned rhodamine-B containing silicamesophase deposited on an oxidized [100)-oriented silicon substrate at aspeed of 2.54 cm/s. FIG. 13A shows a macroscopic pattern formed inseveral seconds by MPL of a rhodamine B-containing solution on ahydrophilic surface. The inset in FIG. 13A shows the correspondingfluorescence image of several adjacent stripes acquired through a 610-nmband pass filter, demonstrating retention of rhodamine-B functionality.

FIG. 13B shows a representative TEM micrograph of a fragment of thepatterned rhodamine-B containing film corresponding to a [110]-orientedcubic mesophase with lattice constant a=10.3 nm. The TEM micrographreveals the ordered pore structure characteristic of a cubic thin filmmesophase.

The sol for this experiment was prepared according to the method ofpresent invention by adding 0.01 wt % rhodamine-B to a silica/4 wt %Brij-56 sol. The TEOS:EtOH:water:HCl:Brij-56:rhodamine-B molarratio=1:22:5.0:0.004:0.065:2.6×10⁻⁵.

EXAMPLE 5

FIGS. 14A, 14B, and 14C shows patterned dot arrays created by inkjetprinting. A comparison is done of the patterns created using standardink on a non adsorbent surface using IJP with the dots created by EISAof the present invention during IJP. Mesoporous spots formed on asilicon substrate by IJP in FIGS. 14B-C are an array of hydrophobicspots made with of a TFTS(1)-modified coating composition of the presentinvention.

FIG. 14A shows an optical micrograph of a dot array created by ink jetprinting of standard ink (from Hewlett-Packard Co., San Diego, Calif.)on a non-adsorbent surface. The resolution is not as good as compared tothe dot array seen in FIG. 14B.

FIG. 14B is an optical micrograph of an array of hydrophobic, mesoporoussilica dots created by evaporation-induced silica/surfactantself-assembly using the coating solution of the present invention duringIJP on an oxidized [100]-oriented silicon substrate followed bycalcination.

A dot fragment prepared as in FIG. 14B was analyzed by TEM. The TEMmicrograph in FIG. 14C shows the ordered mesoporosity of a calcined,fluoroalkylated silica mesophase formed by IJP.

The sol was prepared with molar ratioTEOS:TFTS(1):EtOH:water:HCl:Brij-56 1:0.05:22.0:5.0:0.004:0.065.

The dot pattern used in FIG. 14A and FIG. 14B was designed usingMicrosoft PowerPoint 97 software. The printing rate was approximately 70dots/s and printer resolution 300 dots/inch. The resolution achievedcompared to standard ink and the present invention's ability toselectively functionalize the coating composition suggest applicationsin display technologies.

EXAMPLE 6

Formation of a Patterned Propyl-Amine(3)-Derivatized Cubic Mesophase bySelective De-Wetting Followed by Calcination to Remove the SurfactantTemplates.

Using micro-contact printing or electrochemical desorption techniques,substrates were prepared with patterns of hydrophilic,hydroxyl-terminated SAMs and hydrophobic methyl-terminated SAMs. Thesesubstrates were used for the experiment described in FIG. 8. As shown inFIG. 8 preferential ethanol evaporation during dip-coating caused waterenrichment and selective de-wetting of the hydrophobic SAMs.Correspondingly film deposition occurred exclusively on the patternedhydrophilic SAMs. The sol was prepared by addingaminopropyltrimethoxysilane (NH₂(CH₂)₃Si(OCH₃)₃, APS) to a silica/4 wt %Brij-56 sol, resulting in a final molar ratio ofTEOS:APS:EtOH:water:HCl:Brij-56=1:0.7:22:5.0:0.011:0.065. Selectivede-wetting followed by calcination resulted in a patterned,amine-functionalized, cubic mesoporous film as is evident from theplan-view TEM micrograph, inset A in FIG. 8, showing a [100]-orientedcubic mesophase with a=10.3 nm and nitrogen adsorption-desorptionisotherm as shown in inset B and curve a of FIG. 8 acquired for the thinfilm specimen using a surface acoustic wave (SAW) technique. The TEMmicrograph and surface-acoustic wave-based N₂-sorption isotherm provideevidence of the mesostructural order and proof of the accessibility ofthe mesoporosity to the vapor phase. The dye conjugation reaction wasconducted by immersion in a 0.00002 mM solution of 5,6-FAM, SE (listedin Table 1 of FIG. 6) prepared in dimethylsulfoxide (DMSO) followed byexhaustive, successive washing in DMSO, ethanol, and water. TheSAW-based nitrogen adsorption-desorption isotherm of the dye-conjugatedmesoporous film is shown in inset B, curve b, confirming its poreaccessibility. BET (Brunauer-Emmett-Teller) analyses of the sorptionisotherms indicate that the dye conjugation reaction reduces the surfacearea from 650 to 545 m²/g and the hydraulic radius from 2.2 to 2.1 nm,but pore accessibility is completely retained as evident from combinedTEM, SAW, and fluorescent-imaging results.

In order to make a pH-sensitive fluidic system, the covalently boundpropyl-amine ligands were conjugated with a pH-sensitive dye,5,6-carboxyfl uorescein, succinimidyl ester (5,6-FAM, SE) introduced inthe pore-channel network of the cubic mesophase. After removal of anynon-covalently-bonded dye, the uniform, continuous porosity of theamine-derivatized and dye-conjugated films was confirmed by TEM and thecorresponding SAW-based nitrogen sorption isotherm FIG. 8, Inset B. Theslight reduction in film porosity after dye conjugation reflects thevolume occupied by the attached dye moieties. The patterned,dye-conjugated array was used to monitor the pH of fluids introduced atterminal pads and transported by capillary flow into an imaging cellFIG. 8.

EXAMPLE 7

Patterned pH-Sensitive Fluidic System.

FIG. 15A shows a fluorescence image of three adjacent 5.6-FAM,SE-conjugated pore channel networks after introduction of aqueoussolutions prepared at pH 4.7, 6.6, or 120. Patterned dye-conjugated thinfilm mesophases were prepared as described above in example 5. Aqueoussolutions of varying pH were introduced on the terminal pads FIG. 8 andtransported into the imaging cell by capillary flow. Image was acquiredusing a Nikon Diaphot 300 inverted microscope and 520 nm band passfilter.

FIG. 15B shows the corresponding fluorescence emission spectra of anarray of 5,6-FAM, SE-conjugated mesoporous films upon exposure toaqueous solutions of pH 4.7, 6.6, and 12.0. Shown for comparison arefluorescence spectra of 0.1 micromolar solutions of 5,6-FAM, SE preparedin aqueous solutions of pH 4.7, 6.6, and 12.0. The similarity of the twosets of spectra confirms the maintenance of dye functionality uponconjugation within the mesoporous channel system.

FIG. 15C shows a cross-sectional TEM micrograph of the patterned,dye-conjugated thin film mesophase, providing evidence of the 3-D porechannel network.

Comparison with solution data FIG. 15B indicates that dye moleculescovalently attached to the mesoporous framework retain similarfunctionality to those in solution. The combined fluorescence image asshown in FIG. 15A and cross-sectional TEM micrographs shown in FIG. 15C,of the patterned dye-conjugated film demonstrate the uniformity ofmacro- and mesoscale features achievable by this evaporation-induced,de-wetting and self-assembly route. In comparison, films formed slowly(2-24 hours) by nucleation and growth of thin film mesophases onpatterned SAMs were observed to have non-homogeneous, globularmorphologies unsuitable for fluidic or photonic systems. It is alsonoteworthy that in this case the mesoporous film formed on thehydrophobic regions.

EXAMPLE 7

Functional organosilanes listed in Table 1 of FIG. 6 were incorporatedin the mesophase thin films using the method of the present invention.The pore sizes and surface area were determined from N₂ sorptionisotherms obtained at −196° C., using a surface acoustic wave (SAW)technique. Mass change due to nitrogen sorption was monitored at ˜70pg.cm² sensitivity as a function of nitrogen relative pressure. Poresize and surface area were determined from the isotherms using the BETequation and the BJH algorithm, respectively. Functional groups wereretained through selective surfactant removal during heat treatment innitrogen. TGA and DTA were used to establish the appropriate temperaturewindow enabling complete surfactant removal without silanedecomposition. Five different additives were investigated includingrhodamine-B, cytochrome c (from Fluka), oil blue N, disperse yellow 3(from Aldrich), silver ions and silver nanoparticles. Dye molecule(5,6-carboxyfluorecein succinimidyl ester (5,6-FAM,SE) from MolecularProbes) was conjugated to a thin film mesophase containingaminopropyltrimethoxysilane (APS) to form organosilane 4 in Table 1 ofFIG. 6.

Thin film mesophases containing 3 dimensional networks having 25 Å poresize with a surface area of 750 m²/g made with TFTS are hydrophobic andmay be useful in low k dielectrics applications such as computer chips

Thin film mesophases containing 3 dimensional networks having 25 Å poresize with a surface area of 1060 m²/g made with MPS are useful forcoupling of noble metals and may be useful for applications such ascleaning of noble metal contaminated water.

Thin film mesophases containing cubic patterns having 22 Å pore sizewith a surface area of 650 m²/g made with APS are useful for coupling ofnoble metals, dye, and bioactive molecules and may be useful forapplications such as fabrication of sensors.

Thin film mesophases containing cubic patterns having 21 Å pore sizewith a surface area of 545 m²/g made by conjugating 5,6-FAM, SE dyemolecule to APS are useful for sensing the pH changes and may be usefulfor applications such as microfluidic sensors.

Thin film mesophases containing 3 dimensional networks having 22 Å poresize with a surface area of 560 m²/g made with organosilane 5 of Table 1of FIG. 6, 3-(2,4,-dinitrophenylamino)propyltriethoxysilane.may be serveas chromphores or a non-linear optical materials.

Thin film mesophases containing cubic patterns having 40 Å pore sizewith a surface area of 430 m²/g made with ethane-bridged silsesquioxane,have low k dielectric properties and may be useful for applications suchas computer chips

Rhodamine containing mesophases (refractive index n=1.2-1.3) on aerogeland emulsion-templated thin films (n=1.03-1.10) have been written usingCAD and MPL. The resulting mesophases are useful for directly definingoptical wave-guide structures potentially useful for lasing.

Although the present invention has been fully described in conjunctionwith the preferred embodiment thereof with reference to the accompanyingdrawings, it is to be understood that various changes and modificationsmay be apparent to those skilled in the art. Such changes andmodifications are to be understood as included within the scope of thepresent invention as defined by the appended claims, unless they departtherefrom.

1. A film comprising: a layer having hydrophilic and hydrophobic patterns on a substrate; and a patterned silsequioxane layer substantially deposed exclusively on and contacting the hydrophilic pattern, the patterned silsequioxane layer exhibiting structure and function on at least two length scales made by a film-forming method, said method comprising: providing at least one coating composition comprising: TEOS; a surfactant; at least one organosilane; HCl; water; and ethanol; applying said coating composition on the layer having hydrophilic and hydrophobic patterns to form a patterned coating; and drying said patterned coating to form the patterned silsequioxane film exhibiting structure and function on at least two length scales.
 2. The film of claim 1, wherein said organosilane comprises tridecafluoro-1,1,2,2-tetrahydrooctylriethyoxysilane.
 3. The film of claim 1, wherein said organosilane comprises mercaptopropyltrimethyoxysilane.
 4. The film of claim 1, wherein said organosilane comprises an aminoorganosilane.
 5. The film of claim 1, wherein said organosilane comprises 3-(2,4-dinitrophenylamino)propyltriethoxysilane.
 6. The film of claim 1, wherein said coating composition further comprises a dye.
 7. The film of claim 6, wherein said dye comprises rhodamine B.
 8. The film of claim 1, wherein said surfactant comprises a cationic surfactant.
 9. The film of claim 8, wherein said cationic surfactant comprises cetyl trimethyl ammonium bromide.
 10. The film of claim 1, wherein said surfactant comprises a nonionic surfactant.
 11. The film of claim 10, wherein said nonionic surfactant comprises polyoxyethylene cetyl ether.
 12. The film of claim 1, wherein said surfactant comprises an anionic surfactant.
 13. The film of claim 1, wherein said coating composition is coated on said substrate by dip coating.
 14. The film of claim 1, wherein said coating composition is coated on said substrate by micro-pen lithography.
 15. The film of claim 1, wherein said coating composition is coated on said substrate by ink jet printing.
 16. The film of claim 15, wherein said at least one coating composition comprises a plurality of coating compositions and wherein each of said plurality of coating compositions is stored separately from each other prior to coating each of said plurality of coating compositions on a substrate.
 17. The film of claim 1, wherein providing said coating composition comprises heating an initial composition comprising TEOS, ethanol, water and HCl at a temperature of at least 60° C. for at least 90 minutes.
 18. The film of claim 17, wherein said initial composition contains TEOS, ethanol, water and HCl in the mole ratio of 1:3:7:1:5×10⁻⁵.
 19. The film of claim 17, wherein providing said coating composition further comprises diluting said initial composition with ethanol to provide an ethanol-diluted composition.
 20. The film of claim 19, wherein said initial composition is diluted with 2 volumes of ethanol for every 1 volume of initial composition.
 21. The film of 19, wherein providing said coating composition further comprises diluting said ethanol-diluted composition with water and HCl to provide an acidic sol.
 22. The film of claim 21, wherein providing said coating composition further comprises adding said at least one organosilane to said acidic sol to form a proto-composition.
 23. The film of claim 22, wherein providing said coating composition further comprises adding said surfactant to said proto-composition to form said coating composition.
 24. The film of claim 23, wherein said surfactant is present in said coating composition at a concentration of 0.04 to 0.23 M.
 25. The film of claim 24, wherein providing said coating composition further comprises adding at least one organic additive to said acid sol.
 26. The film of claim 1, wherein said coating composition comprises Si:ethanol:water:HCl:surfactant:organosilane in a mole ratio of 1:22:5:0.004:0.093-0.31:0.039-0.8.
 27. The film of claim 1, wherein said coating is dried at a temperature of 25° C. to 100° C.
 28. The film of claim 1, further comprising removing substantially all of said surfactant from said film.
 29. The film of claim 28, wherein said surfactant is removed by heating said film at a temperature of at least 300° C.
 30. The film of claim 1, further comprising vapor-treating said film with hexamethyldisilazane.
 31. The film of claim 1, wherein said film is mesoporous.
 32. The film of claim 1, wherein said film has a thickness of 50 nm-1 μm.
 33. A film made by a film-forming method, said method comprising: providing at least one coating composition comprising: TEOS; a surfactant; at least one organosilane; HCl; water; and ethanol; applying said coating composition on a substrate to form a coating on said substrate; and drying said coating to form a patterned silsequioxane film, wherein said organosilane comprises aminopropyltnmethoxysilane.
 34. The film of claim 33, wherein said coating composition further comprises a dye coupled to aminopropyltrimethoxysilane.
 35. A film made by a film-forming method, said method comprising: providing at least one coating composition comprising: TEOS; a surfactant; at least one organosilane; HCl; water; and ethanol; applying said coating composition on a substrate to form a coating on said substrate; and drying said coating to form a patterned silsequioxane film, wherein said organosilane comprises (H₅C₂O)₃SiCH₂CH₂Si(OC₂H₅)₃.
 36. A film made by a film-forming method, said method comprising: providing at least one coating composition comprising: TEOS; a surfactant; at least one organosilane; HCl; water; and ethanol; applying said coating composition on a substrate to form a coating on said substrate; and drying said coating to form a patterned silsequioxane film, wherein said surfactant comprises an anionic surfactant, wherein said anionic surfactant comprises sodium dodecyl sulfate.
 37. A film made by a film-forming method, said method comprising: providing at least one coating composition comprising: TEOS; a surfactant; at least one organosilane; HCl; water; and ethanol; applying said coating composition on a substrate to form a coating on said substrate; and drying said coating to form a patterned silsequioxane film, wherein said coating composition comprises Si:ethanol:water:HCl:surfactant:organosilane:organic additive in a mole ratio of 1:22:5:0.004:0.093-0.31:0.039-0.8:2.6×10⁻⁵.
 38. A film made by a film-forming method, said method comprising: providing at least one coating composition comprising: TEOS; a surfactant; at least one organosilane; HCl; water; and ethanol; applying said coating composition on a substrate to form a coating on said substrate; and drying said coating to form a patterned silsequioxane film, wherein said at least one organosilane comprises (H₅C₂O)₃SiCH₂CH₂Si(OC₂H₅)₃ and said coating composition comprises Si:EtOH:H₂O:HCl surfactant in a mole ratio 1:22:5:0.004:(0.054-0.18). 